Their reasoning being that they are coding and calibrating for a only a couple of devices (4/4s, 5?), it should work reasonably well. Does iOS allow for complete control of the camera h/w? I presume setting the focus point to an arbitrary 'near' to spread out the incoming light, and having complete control of the camera's exposure/gain settings is along the lines of standardizing a reading.

Sounds interesting but my initial thought is that looking at the screen of the iPhone, even with its screen as dim as possible, and with a red cover, will involve some loss of dark adaptation. That's one of the reasons I like the Unihedron SQM - one only has to look at the illuminated readings, not a full screen.

But my reservations are only imagined at this point and the app may have taken care of all this so I'm eager to see what it's really like.

My concern is this. Can these cameras obtain an image of a fairly dark sky which is not mostly noise? The chip's pixels are awfully small, and moreover are reduced in efficiency because of the Bayer mask. One must have some minimum signal to noise ratio in order to derive a meaningful measurement allowing to discriminate brightness differences to the desired degree.

I have been testing the app. As of the last test I ran a few days ago, it's results are under what the SQM gives you. The developer says that there is a difference between what the iPhone4 and iPhone5 camera gives you. Hopefully this evening I can try the latest release to see if its results are more consistent with the SQM.

Of greater interest to me is not the fact that currently this app is "under" the SQM reading, which I presume to mean is a consistently lower (brighter?) reported value, but whether the readings track reasonably closely. And whether the level of discrimination is reasonably fine. And whether the readings are reasonably repeatable. And whether results extend to at least moderately dark sky levels.

Down to about 21 MPSAS, to be useful at all the 1-sigma error should not exceed 0.2 magnitude.

Without specifically addressing the quality of the iPhone app, I would like to mention that SQM are used for many reasons. My observatory uses two SQM-LE for full-time monitoring purposes; To provide info on current conditions to active observers, and also for generating long-term records.

We are developing the app. The app will hit the app store as soon as all devices with a decent camera are supported. The devices with good (close) results are the iPhone 4S and 5. We hope to support the 4's camera as well as the iPad 3rd gen and iPad mini cameras. We are working close with the IDA and will distribute a special 'lite' version soon. The lite version works like a SQM, but has not the Mag/square sec arc scale. It will be more aimed towards a broad audience, submitting as many readings as possible. This should (hopefully) generate a lot of useful readings. The app is more than a reader: it submits device position (aimed at the zenit), GPS and moon readings.For amateur astronomers like you there will be a pro version (in app or separate build) with proper SQM readings, google like darkness map (pinpoints of you and other dark sky meter user with SQM readings) and a GFS based clear sky clock.Currently we are testing and getting close to releasing the app. Hopefully in April.

Thanks for chiming in, and developing the app! If it isn't too much trouble or leaking 'programming secrets', could you share some insights into how you might have overcome some of the perceived issues using a iPhone's camera to do the work? I'm a little weary if the eventual results is subject to larger-than-expected variations due to iPhone H/W and iOS constraints/limitations, and all the data being fed to IDA ends up being affected.

That sounds like a really good app that'll have great effects on reducing light pollution. I can't wait to try it out.

How will this app have great effects on reducing light pollution? It won't affect those that don't care about the night skies, and have bright yard lights, etc.; nor city light pollution. Just curious as to how this might benefit in reducing LP.

I agree. It allows me to gather data that I can put into a coherent product for the masses. For instance, I could ask to have the streetlights turned off in my neighborhood, gather some data using this tool, then get the same data points (using GIS systems) with the lights on to demonstrate what an effect it has on my skies. In addition, just from a 'neighbor' standpoint, I can show them what an effect leaving on a giant flood light has on my skies too.

You're right, the app won't magically reduce light pollution. But, it gives you easy access to data that can be used to aid the cause. And, if the app is priced right, it'll give us access to many more data points than we've had easy access to in the past. Finally, I'm assuming it's tied into some IDA database. This allows the IDA to gather local decentralized data from anyone with an Android/iOS device. That's a huge number of people these days. Even if you take into account AA's are a small number of those people, I guarantee you that the majority of us are using smart phones... ready access to volunteers to collect data is nice.